I have the data below
   a   b
1  12  1
2  14  2
3  12  3
4  12  3
5  14  1
6  12  4
I have to group the data according to the column (a)..after which i have to delete the rows which has the same (b) value. Below i have shown what it should look like,
   a   b
1  12  1
2  12  4
3  14  1
4  14  2
is there any easy way in pandas to do this?